The present invention is directed to an internal expansion coupling device that can be joined in an essentially infiltration/exfiltration (I/E) free system, such as a pair of tubular members, where said tubular members are intended for the transmittal of a fluid medium under pressure or freeflow gravity systems.
With a very hard look now being taken with the environment, such as the numerous laws and regulations dealing with the air and clean water, the EPA is looking into the I/E rates of our nation's sewer systems. The United States has millions of miles of sound sewer pipe jointed with cement mortar or asphalt that shrinks or cracks. This and other defects allow excessive infiltration into the system, causing problems in the treatment of sewage or exfiltration in close proximity to water supply lines and streams, both I/E become a threat to the quality of our water supply.
The above represents just one need, albeit critical, where a sound and effective coupling system is essential. There are numerous other systems, such as the transmission of a fluid medium under pressure, i.e. water, oil, chemicals, where field maintenance and repair is required. Thus, a coupling system must not only be fluid tight, but relatively easy to install and/or retrofit in the field. Additionally, the coupling system hereof is particularly suitable for thin-walled pressurized fluid conduits and piping systems such as irrigation systems, water transmission systems, and various other gas and fluid transport systems. The internal expansion coupling is also suitable for heating and ventilating ducting systems.
Essentially, two types of coupling devices have been developed, external or contraction devices, and internal or expansion devices. The present invention is directed to the latter category. One problem discovered therein with such prior art devices is the difficulty of being able to force the coupling member into the tubular member to be joined, particularly with larger sized tubular members. The present invention provides a means to readily achieve this jointure, and will become more apparent in the detailed description which follows.
Notwithstanding the needs and problems noted previously, there have been attempts by the prior art to make effective internal joint connections. For example, in U.S Pat. No. 4,478,434 to Little, there is taught a system for coupling adjacent ends of flexible tubular members comprising an elongated open ended tube member having an O.D. that is approximately the same as the I.D. of such flexible tubular members. More particularly, such system includes a transverse slit across said open ended tube member, and a pair of aligned strap-like members having opposite ends thereof connected to said tube members on opposite sides of the slit. Threadable means, as part of the strap-like members, join the opposite ends of the tube member whereby said tube may be contracted a limited amount, or expanded.
Other internal expanding coupling means are taught in U.S. Pat. No. 3,514,135 to Cooper consisting of a split sleeve having oppositely disposed inclined longitudinal flanges which may be radially moved to expand the sleeve; U.S. Pat. No. 3,141,687 to Broberg et al for a steel band splicing strap with a threaded member to separate the strap ends; U.S. Pat. No. 3,394,951 to Crivello for a polyethylene conduit insert consisting of a pair of spaced, axially extending coupling portions and a radially outwardly extending central portion. Each of the coupling portions has a substantially cylindrical internal surface and a pair of opposed frustoconical exterior surfaces tapered at approximately 2.degree. and separated by an annular groove with the portions of the frustoconical surfaces of greatest diameter being adjacent the groove; and U.S. Pat. No. 3,269,754 to Bertling et al, a device similar in operation or function to Crivello.
Certain of the above devices are open to the objections that they create excessive internal diameter restrictions; that they are difficult to manipulate; that they require the use of special skills and or tools to connect and disconnect; that they require strict inside pipe diameter tolerances in order to form a sealed union; that they are lacking in gasket sealing integrity under field conditions; that they fail under high internal pressures; and, that they are lacking in flexibility.
The coupling device of this invention overcomes such objections. The coupling device, when in the contracted condition can be easily inserted into the pipe ends, and when in an expanded condition exhibit a minimum restriction while providing an excellent joint. The coupling can be reused in its entirety. Thus, the present invention teaches an internal expansion coupling device which is more versatile than those of the prior art, and is very effective against leaks thereof by its ability to utilize the internal forces or pressures of the medium being transmitted therethrough. This, among such other features, namely, to provide an excellent seal between adjacent pipes within a wide latitude of I.D. tolerances; to provide a coupling which maintains sealing ability under field conditions, when damage occurs to both inside and outside pipe walls, as in the form of nicks and scratches; to provide a coupling that will sustain high internal pressures while enduring both pipe and coupling deflections; to provide a coupling which will function under negative internal pressures; to provide a coupling which is economical to manufacture and inexpensive to use; to provide a coupling that is resistive to corrosive fluids; to provide a coupling which exhibits long in-service life, will become more apparent from the further description, particularly when read in conjunction with the accompanying drawings.